The present invention relates to a method of and apparatus for linking microinstructions to be executed in a control memory of a microprogrammed computer. In particular, the invention relates to microinstruction linking control arrangements including a provision for overlap between the execution of a current microinstruction and the phase of preparing for the next microinstruction to be executed. The invention is applicable to systems for processing or transmitting data and is of particular utility in large computer systems where tests relating to linking microinstructions together take significant time and often are completed too late in a microinstruction execution cycle to be considered. In computers which operate in the overlap mode, this delay in preparing for a microinstruction results in missed execution of the microinstruction.